The present invention relates generally to a vehicle exhaust system, and more particularly to a system and method for cooling exhaust gasses before exiting the vehicle exhaust system.
Recent emissions regulations for vehicles employing diesel engines limit the amount of soot that the vehicles may emit. The soot is produced as a by-product of the combustion of the diesel fuel and is carried out with the vehicle exhaust. Diesel particulate filters (also called traps) added to the exhaust system limit the soot emissions in order to meet the regulations.
Diesel particulate filters work by collecting the soot while allowing the exhaust gasses to pass through. As the vehicle operates, then, the soot builds up in the filter. This soot needs to be periodically eliminated from the filter in order to assure that the filter does not become clogged. A clogged filter can potentially cause damage to itself or the engine. The soot that builds up in the filter can be removed through a process called regeneration.
Regeneration is performed by heating the diesel particulate filter to a high temperature to burn away (incinerate) the soot, thus cleaning out the filter. However, during regeneration, the heat used to cause the regeneration process may cause the exhaust gasses to be expelled out of the tailpipe at higher temperatures than is desirable, as well as make the exhaust skin temperature higher than is desirable. Thus, it is desirable to cool the high temperature exhaust gasses that occur during regeneration before they are expelled from the exhaust system.